Field of the Invention
The present invention relates to the field of image display technologies, and particularly, to a WOLED back panel and a method of manufacturing the same.
Description of the Related Art
In the display technologies using an organic light-emitting diode (OLED) having a self-luminous characteristic, a very thin coating of organic material and a glass substrate are used, and the organic material will luminesce when a current passes therethough. The OLED has many advantages such as active luminescence, a high luminous efficiency, a fast response time (in order of 1 μs), a low operating voltage (3˜10V), a wide angle of view) (>170°), a small panel thickness (<2 mm), a low power consumption, a broad range of operating temperature (−4° C.˜85° C.), a flexible display and the like, and thus has been known as the third generation display technology after CRT and LCD. The OLED may be made by many production processes such as small molecular evaporation, polymer spin coating, ink jet printing, large area printing or the like, and be suitable for mass production with low production costs, and thus may compete with a fluorescent lamp in the long run. A white organic light-emitting diode (WOLED) is of a surface light source, may be made into a flat light source having a large area and any shape when compared to a point source of LED, and thus is more suitable to a backlight source of a liquid crystal display and a full color OLED display. Because of a huge potential of the WOLED in flat panel lighting applications, the WOLED has become a hot research topic in the 10 years, and is expected to play a main role in new semiconductor lighting technologies, like the LED.
A basic arrangement of the OLED is a structure like a sandwich, formed by a thin and transparent layer of indium tin oxide (ITO) having semiconductor properties and connected with an anode of a power supply, and a metal cathode. The whole arrangement comprises a hole transmission layer (HTL), a light emitting layer (EL) and an electron transmission layer (ETL). When applied with suitable voltages by the power supply, positive holes and negative charges will combine within the light emitting layer to produce the light, and thus three-primary colors including red R, green G and Blue B may be produced depending on different compositions, so as to constitute basic colors. The OLED is characterized, firstly, in self-luminescence and needing no backlight compared to TFT LCD, and thus is high in visibility and brightness. Secondly, the OLED requires a low voltage and has a high energy-saving efficiency, a fast response, a light weight, a thin thickness, a simple configuration, a low cost and the like, and thus is regarded as one of the most promising products in the 21st Century.
FIG. 1 (a) is a schematic appearance diagram of a typical bottom-gate and bottom-emitting type WOLED back panel in the prior art. As shown in Fig. (a), the WOLED back panel comprises a plurality of sub-pixel units arranged in an array, and each sub-pixel unit includes a pixel electrode 101 and a via region 102 for connecting a drain of an underlying thin film transistor (TFT) 110 and an upper pixel electrode 101. FIGS. 1(b)˜1(e) show schematic flowcharts of a process of manufacturing the AA′ section of the WOLED back panel shown in Fig. (a). The specific process is described as follows.
The process of manufacturing an oxide bottom-gate TFT is similar to a process of manufacturing a-Si. The difference between the two processes is that in the process of manufacturing an oxide bottom-gate TFT, a material for an active layer is changed, and an etching stop layer (ESL) is added after forming the active layer so as to prevent the active layer from being damaged when etching a source/a drain. Thus, the specific process of manufacturing the oxide bottom-gate TFT will not be expanded and described in details, and only a process of manufacturing a color filter array (COA) after depositing a passivation layer is illustrated.
Firstly, after depositing a passivation layer (PVX) 111, color filters 103 are spin-coated in a color filter production line in order of RGB of the sub-pixels, as shown in FIG. 1(b). Since the color filters 103 have a larger thickness, it is required to flatten the color filters 103 by depositing a planarization layer 104, so as to ensure continuity of a subsequent ITO film between the via 102 and the pixel electrode 101, as shown in FIG. 1(c). Then, after exposure and curing processes, an ITO film 105 is deposited and etched, as shown in FIG. 1(d), so that the ITO film is evenly laid above the color filters 103 covered with the planarization layer 104. Thereafter, in order to ensure that light emitted from each sub-pixel will not interfere with the other sub-pixels, pixel defining layers 106 are manufactured among respective sub-pixels, such as DPI000, which have a thickness of 1.5˜2 μm, thereby forming a structure shown in FIG. 1(e). The organic light emitting layer of the WOLED back panel may be deposited on pixel electrodes between the pixel defining layers 106 by evaporation or printing, and then a metal cathode material such as Al is deposited, finishing manufacturing the back panel.
It is obvious that the process of manufacturing the WOLED back panel is relatively complicated in the prior art, processes such as gluing, exposing and the like are required to manufacture the pixel defining layer, and a special mask for the pixel defining layer needs to be made, causing a long production cycle and a higher cost.